Weight measuring equipment and crew weight measuring equipment comprising it

ABSTRACT

A weight measuring equipment comprising a base fixed to an object, a strain detection substrate fixed to the base, a fitting pin fixed to the strain detection substrate, an arm rotatably attached to the base by a support pin, and a leaf spring with one end fixed to the arm and the other end supported by the fitting pin. The weight measuring equipment further comprises a second arm with one end receiving the load of the object to be measured and the other end fixed to the arm through a link pin. By the configuration of the present invention, the load applied to the strain detection substrate is reduced, and a weight measuring equipment improved in detecting resolution is obtained. Furthermoe, the weight measuring equipment of the present invention is unitized, and the equipment can be easily built in various equipments.

TECHNICAL FIELD

[0001] The present invention relates to a weight measuring equipment formeasuring weights of objects, and a driver and a passenger (hereinafterreferred to “a person”) weight measuring equipment for vehicles usingsame.

BACKGROUND ART

[0002] Recently, in a weight measuring equipment, for example, a personweight measuring equipment for vehicles in particular, there is a trendof controlling an operation of safety equipment according to a weightand constitution of a person's body in order to improve a performance ofsheet belts and air bags. For example, the vehicle judges whether theperson getting therein is a child or an adult, and adjusts an expandinggas quantity and an expanding speed or stops the operation of the airbag. Therefore, it is necessary to know the weight of the person sittingon the seat by using some means. As an example of such means, a systemis proposed in that a strain sensor (load cell) is disposed at fourcorners of seat rails in order to measure the weight of the person byadding the loads vertically applied to the load cell (Japanese PatentLaid-open Publication H11-1153).

[0003] As for a strain sensor for the person weight measuring equipment,there is a demand for a small-sized sensor whose maximum measuring loadis about 50 kg. As such strain sensors, there are those having a straingauge stuck (or formed) on a sensor plate which is deformed by the load,those based on a piezoelectric system, and those using a static capacitysensor for detecting the displacement of an elastic member which isdeformed by the load.

[0004] In a case of such weight measuring equipment and a person weightmeasuring equipment using same, the load of the object to be measured isdirectly applied to the strain detectors disposed in the equipment.Therefore, there arises a problem of decrease in a detecting resolutionif priority is given to an assurance of a strength of the detectors.

[0005] The present invention is intended to address such problem, andthe object of the invention is to provide a weight measuring equipmentand a person weight measuring equipment using the same. The weightmeasuring equipment can improve the detecting resolution by reducing theload applied to the strain detector as much as possible.

DISCLOSURE OF THE INVENTION

[0006] The weight measuring equipment of the present invention comprisesa base fixed to an object, a strain detection substrate attached to thebase, a fitting pin attached to the strain detection substrate, an armrotatably attached to the base by a support pin, and a leaf spring withone end attached to the arm and the other end supported by the fittingpin. Also, the weight measuring equipment of the present inventionfurther comprises a second arm with one end receiving the load of theobject to be measured and the other end connected to the arm by a linkpin. By the configuration of the present invention, a weight measuringequipment reduced in the load applied to the strain detection substrateand improved in detecting resolution is obtained. Also, the measuringequipment of the present invention is unitized and can be easily builtin various types of equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is an exploded perspective view of a first preferredembodiment of the present invention.

[0008]FIG. 2 is a side sectional view of the first preferred embodimentof the present invention.

[0009]FIG. 3 is a plan view of the first preferred embodiment of thepresent invention.

[0010]FIG. 4 is an exploded view of a second preferred embodiment of thepresent invention.

[0011]FIG. 5 is a side sectional view of the second preferred embodimentof the present invention.

[0012]FIG. 6 is a plan view of the second preferred embodiment of thepresent invention.

[0013]FIG. 7 is a partly detailed view for describing the operation ofan arm.

[0014]FIG. 8A is a front view of a fitting pin showing anotherconfiguration of the second preferred embodiment of the presentinvention.

[0015]FIG. 8B is a side view of another configuration of the secondpreferred embodiment of the present invention.

[0016]FIG. 8C is a partly detailed view of another configuration of thesecond preferred embodiment of the present invention.

[0017]FIG. 9A is a front view of a fitting pin showing still anotherconfiguration of the second preferred embodiment of the presentinvention.

[0018]FIG. 9B is a side view of still another configuration of thesecond preferred embodiment of the present invention.

[0019]FIG. 9C is a partly detailed view of still another configurationof the second preferred embodiment of the present invention.

[0020]FIG. 10 is an exploded perspective view of a third preferredembodiment of the present invention.

[0021]FIG. 11 is a side sectional view of the third preferred embodimentof the present invention.

[0022]FIG. 12 is a plan view of the third preferred embodiment of thepresent invention.

[0023]FIG. 13 is an exploded view of a fourth preferred embodiment ofthe present invention.

[0024]FIG. 14 is a side sectional view of the fourth preferredembodiment of the present invention.

[0025]FIG. 15 is a plan view of the fourth preferred embodiment of thepresent invention.

[0026]FIG. 16A is a front view of a fitting pin showing anotherconfiguration of the fourth preferred embodiment of the presentinvention.

[0027]FIG. 16B is a side view of another configuration of the fourthpreferred embodiment.

[0028]FIG. 17A is a front view of a fitting pin showing still anotherconfiguration of the fourth preferred embodiment of the presentinvention.

[0029]FIG. 17B is a side view of still another configuration of thefourth preferred embodiment of the present invention.

[0030]FIG. 18 is an exploded perspective view of a fifth preferredembodiment of the present invention.

[0031]FIG. 19 is a side sectional view of the fifth preferred embodimentof the present invention.

[0032]FIG. 20 is a plan view of the fifth preferred embodiment of thepresent invention.

[0033]FIG. 21A is a front view of a fitting pin showing anotherconfiguration of the fifth preferred embodiment of the presentinvention.

[0034]FIG. 21B is a side view of another configuration of the fifthpreferred embodiment of the present invention.

[0035]FIG. 22A is a front view of a fitting pin showing still anotherconfiguration of the fifth preferred embodiment of the presentinvention.

[0036]FIG. 22B is a side view of still another configuration of thefifth preferred embodiment of the present invention.

[0037]FIG. 23 is an exploded perspective view of a sixth preferredembodiment of the present invention.

[0038]FIG. 24 is a side sectional view of the sixth preferred embodimentof the present invention.

[0039]FIG. 25 is a plan view of the sixth preferred embodiment of thepresent invention.

[0040]FIG. 26 is an exploded perspective view of a seventh preferredembodiment of the present invention.

[0041]FIG. 27 is a side sectional view of the seventh preferredembodiment of the present invention.

[0042]FIG. 28 is a plan view of the seventh preferred embodiment of thepresent invention.

[0043]FIG. 29 is a side view illustrating a seat for vehicles furnishedwith any one of the weight measuring equipments of the first throughseventh embodiments of the present invention.

BEST MODE FOR CARYING OUT THE INVENTION

[0044] First Preferred Embodiment

[0045] The weight measuring equipment (hereafter referred to as“equipment”) in the first preferred embodiment of the present inventionwill be described with reference to FIG. 1 through FIG. 3. FIG. 1 is anexploded perspective view of the present preferred embodiment. FIG. 2 isa side sectional view of the present preferred embodiment. FIG. 3 is aplan view of the present preferred embodiment.

[0046] In FIG. 1, strain detection substrate 2 is fixed to base 1, whichis to be fixed to an object (not shown), with screws 5 a, 5 b, 5 c, 5 dscrewed into tapped holes 4 a, 4 b, 4 c, 4 d through holes 3 a, 3 b, 3c, 3 d. Hole 6 as a point of action at which the load is applied isprovided at a point where a straight line connecting the fixing holes 3a and 3 d crosses a straight line connecting the holes 3 b and 3 c.Slots 7 for generating a strain of a detectable level, and strainresistor 8 whose resistance varies depending upon the amount of strainare formed around the hole 6.

[0047] Fitting pin 9 is made of a material that withstand more load thanthe measuring load, and at an end thereof is formed threaded portion 9a, and at a hexagonal head 9 c is formed insert portion 9 b. Also, thefitting pin 9 is inserted into the hole 6 of the strain detectionsubstrate 2 and fixed by nut 10. And the base 1 is provided with reliefhole 1 d.

[0048] Arm 19 is provided with hole 16, and is rotatably supported bysupport pin 22 between rotation support holes 16 a and 16 b formed inthe side wall of the base 1. Also, slide holes 19 c, 19 d arerespectively formed in wing portions 19 a and 19 b extending from oneend of the arm 19. Second arm 21 is made from a plate material generallyU-shaped, which receives the load of the object to be measured and isvertically movable. Holes 21 c, 21 d are respectively formed in bentwing portions 21 a, 21 b so that link pin 18 passes therethrough and thesecond arm 21 can rotate. With the link pin 18 inserted through theslide holes 19 c, 19 d and holes 21 c, 21 d, the second arm 21 isrotatably supported along with the arm 19.

[0049] At one end of leaf spring 13 are disposed fixing holes 13 a, 13 bin positions corresponding to tapped holes 14 a, 14 b of the arm 19, andat another end thereof is disposed U-shaped notch 13 c. The notch 13 cis inserted to the insert portion 9 b of the fitting pin 9. Also, theleaf spring 13 is designed so as to be provided with specific springcharaasteristics according to the measuring load.

[0050] A method of assembling these components will be described in thefollowing.

[0051] First, the fitting pin 9 is fixed to the strain detectionsubstrate 2 by using the nut 10. Next, the strain detection substrate 2is fixed to the base 1 by using the screws 5 a to 5 d. Also, the leafspring 13 is fixed to the arm 19 with screws 23 a, 23 b. Further, thearm 21 is connected to the arm 19 by using the link pin 18. In thisstate, the U-shaped notch 13 c of the leaf spring 13 is inserted to theinsert portion 9 b of the fitting pin 9, and the arm 19 is supported bysupport pin 22 on the base 1. The support pin 22 is fixed by nut 23.

[0052] The operation of the equipment will be described in the followingwith reference to FIG. 2.

[0053] When the weight of the object to be measured is applied via thearm 21 of the equipment assembled as described above, a force acts onthe arm 21 to move it downward about the support pin 22 as a fulcrum.The force is transferred via the arm 19 to move the leaf spring 13upward. This works as a force to pull up the fitting pin 9 fixed to thestrain detection substrate 2, generating a strain in the straindetection substrate 2 according to the pulling force. Since theresistance of strain resistor 8 canges according to the strain, thechange of the resistance is computed in processing circuit 30 to measurethe load. To achieve the purpose that a strain is generated in thestrain detection substrate 2 but the strain detection substrate 2 ishardly deformed, the leaf spring 13 deforms so that the deformation dueto the weight of the object to be measured via the arm 21 is absorbed bythe leaf spring 13.

[0054] In this case, the ratio of the distance between the fitting pin 9and the support pin 22 and the distance from the support pin 22 to thelink pin 18 is freely variable, and therefore, it is possible to greatlyreduce the load applied to the strain detection substrate 2 in order toenhance the detecting resolution.

[0055] Particularly, by increasing the ratio of the distance between thefitting pin 9 and the support pin 22 and the distance from the supportpin 22 to the link pin 18 two times or more, it is possible to furtherreduce the load applied to the strain detection substrate 2 and to moreimprove the load detecting resolution.

[0056] Also, since the equipment of the present preferred embodiment isunitized, it is easy to build the equipment in various types ofequipment. Further, the number of assembling steps can be reduced, andit is unnecessary to adjust a sensor characteristics at a time ofassembly.

[0057] The above configuration involves no problem in the case of normalweight measurement, but when a load exceeding the maximum measuring loadis applied to the equipment via the arm 21, the load is also applied tothe leaf spring 13 and strain detection substrate 2. As a result, thereis a possibility of permanent deformation or damage of the leaf spring13, or breakdown of the strain detection substrate 2. As acountermeasure, a possible method is to increase withstandcharacteristics of the leaf spring 13 and strain detection substrate 2.However, increasing the withstand characteristics of leaf spring 13causes the equipment to increase in size, and increasing the withstandcharacteristics of strain detection substrate 2 decreases the amount ofstrain with respect to the load in the measuring range, resulting inlowering of the measuring resolution.

[0058] In order to address the above problems, as shown in FIG. 1, thewing portion 21 a, 21 b of the arm 21 is partly provided with projection21 e, 21 f facing toward the base 1, and when the second arm 21 rotatesabout the support pin 22 to move down, reaching a specific stroke, thenthe arm comes into contact with the bottom plate 1 c of the base 1. Inthis case, the stroke is generally designed to be 2 mm in connectionwith the maximum measuring load. On the other hand, when a load to atensile direction is measured, projection 19 e and 19 f disposed at endsof the arm 19 and facing toward the base 1 come into contact with thebottom plate 1 c of the base 1. The stroke is similarly designed to be 2mm.

[0059] In the above configuration, when the load exceeds the maximummeasuring load, a stopper is formed between the projections 21 e, 21 fdisposed on the arm 21 or the projections 19 e, 19 f disposed on the arm19 and the bottom plate 1 c of the base 1. Accordingly, even when a loador impact load exceeding the maximum measuring load is applied, thestopper structure receives the load, and thereby, makes it is possibleto prevent the breakdown of strain detection substrate 2 and leaf spring13.

[0060] Further, the dimensions in the widthwise direction(right-and-left direction in FIG. 1) and lengthwise direction(back-and-forth direction in FIG. 1) of the notch 13 c formed in theanother end of leaf spring 13 are set larger than the diameter of theinsert portion 9 b of the fitting pin 9. The purpose is to prevent aforce from being directly applied to the insert portion 9 b of thefitting pin 9 when an abnormal force is applied to the object to bemeasured or to the equipment, in back-and-forth direction, or inright-and-left direction, during the measurement or at standby mode ofthe equipment. For example, when such abnormal load is supposed to be animpact load caused due to a collision of vehicles, the load then appliedis 2,000 kg or more. Even in that case, the equipment of the presentpreferred embodiment will not break down due to the durability of thesupport pin 22 and the base 1, and in the course of impact application,the impact is absorbed as the support pin 22 and each structure deformea little. The size of the notch 13 c of leaf spring 13 is decided so asto provide a clearance according to such deformation. Thus, it ispossible to prevent the breakdown of the strain detection substrate 2even when impacts are applied to the equipment from the back-and-forthand the right-and-left direction.

[0061] Second Preferred Embodiment

[0062] The weight measuring equipment (hereafter referred to equipment)in the second preferred embodiment of the present invention will bedescribed with reference to FIG. 4 to FIG. 9.

[0063] In FIG. 4, U-shaped base 1 is fixed by bolt 51 to an object suchas a chassis 50. Side plates 1 a, 1 b is provided with rotation supportholes 16 a, 16 b for the support pin 22, and guide holes 17 a, 17 b forthe link pin 18. Bottom plate 1 c is provided with tapped holes 4 a, 4b, 4 c, 4 d for fixing the strain detection substrate 2, and the reliefhole 1 d for threaded portion 9 a of the fitting pin 9 and the nut 10.

[0064] The structure, arrangement, and function of the strain detectionsubstrate 2, the fitting pin 9, and the leaf spring 13 are the same asthose in the first preferred embodiment.

[0065] The arm 19 is provided with the hole 16, and is rotatablysupported by the support pin 22 between the rotation support holes 16 a,16 b formed in the side plates 1 a, 1 b of the base 1, which does notslip off due to threaded portion 22 a formed at the end of the supportpin 22, and the nut 23. Also, the wing portions 19 a, 19 b extendingfrom one end of the arm 19 is respectively provided with slide holes 19c, 19 d for guiding the link pin 18 so that the pin moves in thehorizontal direction. Further, the projections 19 e, 19 f facing towardthe bottom plate 1 c of the base 1 are disposed at the end of the arm19.

[0066] The second arm 21 receives the load of the object to be measuredand is vertically movable and is formed of U-shaped plate material. Thelink pin 18 goes through the holes 21 c, 21 d formed in the bent wingportions 21 a, 21 b of arm 21, the slide holes 19 c, 19 d of arm 19, andthe guide holes 17 a, 17 b, or slots for guiding the pin vertically,disposed in the side plates 1 a, 1 b of the base 1. The link pin 18 isprovided with an E-ring, which is not shown, to prevent the link pin 18from slipping off. Also, the wing portions 21 a, 21 b are partlyprovided with the projections 21 e, 21 f facing toward the bottom 1 c ofthe base 1.

[0067] A method of assembling these components is described in thefollowing.

[0068] First, the fitting pin 9 is fixed to the strain detectionsubstrate 2 by using the nut 10. Next, the strain detection substrate 2is fixed to the base 1 with screws 5 a, 5 b, 5 c, 5 d. Also, the leafspring 13 is fixed to the arm 19 with screws 23 a, 23 b. The U-shapednotch 13 c of the leaf spring 13 is inserted into the insert portion 9 bof the fitting pin 9, and the arm 19 is supported by the support pin 22on the base 1. The support pin 22 is fixed by nut 23. Further, the slideholes 19 c, 19 d of the arm 19, the holes 21 c, 21 d of the arm 21, andthe guide holes 17 a, 17 b of the base 1 are aligned to each other,through which the link pin 18 is inserted and attached to the arm 19,and an E-ring or the like is attached to prevent the pin from slippingoff.

[0069] Next, the operation of the equipment is described with referenceto FIG. 5 and FIG. 6. FIG. 5 is a sectional view of the equipmentcompleted as described above and mounted on a seat truck 45 of a vehicleseat and a chassis 50, and FIG. 6 is a plan view of the equipment.

[0070] In FIG. 5, when the weight of the object to be measured isapplied to the arm 21, a force acts on the arm 21 to move it downwardabout the support pin 22. The force is transferred via the arm 19 tomove the leaf spring 13 upward. This works as a force to pull up thefitting pin 9 fixed to the strain detection substrate 2, generating astrain in the strain detection substrate 2 according to the force. Sincethe resistance of the strain resistor 8 changes with the strain, thechange of the resistance is computed in the processing circuit 30 tomeasure the load. To achieve the purpose that the strain occurs in thestrain detection detection substrate 2, but it is but hardly deformed,the leaf spring 13 deforms so that the deformation due to the weight ofthe object to be measured via the arm 21 is absorbed by the leaf spring13.

[0071] Particularly, at the link mechanism portion where the arm 21 andthe arm 19 are rotatably connected by the link 18, a locus deviation ofthe linear motion in the vertical direction of arm 21 from the circularmotion of the arm 19 about the link pin 18 is mechanically buffered.This mechanism is described in the following with refeence to FIG. 7.

[0072] For example, when the arm 21 is displaced downward by Y with aload applied thereto, the arm 19 is accordingly rotated by angle A withturning radius R about the shaft 22. At the time, the locus of the arm21 is linear, while the locus of the arm 19 is circular, and therefore,locus deviation X is generated as shown in FIG. 7. Here, an angle A dueto the displacement Y and the resultant deviation X are determined bythe following equations 1 and 2.

A=sin⁻¹(Y/R)  (1)

X=R cos(sin⁻¹(Y/R))  (2)

[0073] Lengthwise dimensions of the slide holes 19 c, 19 d aredetermined in anticipation of the X. Also, lengthwise dimensions of theguide holes 17 a, 17 b are determined taking into account of the strokeof arm 21. In this way, it is possible to reduce a detection errorsuperposed on the load. The error occurs when a frictional force isgenerated on the slideway by an elastic repulsion due to the locusdeviation, and the frictional force is superposed on the load. And it isalso possible to reduce a hysteresis on a characteristic curve. In thisway, a highly accurate equipment is obtained.

[0074] Also, as shown in FIG. 8A and FIG. 8B, as a front view and a sideview of the fitting pin 9, the fitting pin 9 may have an arcuate innerwall at the insert portion 9 b. Thus, as shown in FIG. 8C, the loadacting portion is linearly concentrated, reducing the variation inacting position of the load transferred to the fitting pin 9, therebyimproving the detection accuracy.

[0075] Also, as shown in FIG. 9A and FIG. 9B as the front view of andthe side view of the fitting pin 9, the fitting pin 9 may have asemicircular inner wall at the insert portion 9 b. Thus, as shown inFIG. 9C, the load acting portion is linearly concentrated, reducing thevariation in acting position of the load transferred to the fitting pin9, thereby improving the detection accuracy. The resultant effect issame as the fitting pin 9 shown in FIG. 8, but the detection accuracy isfurther improved because of suppressing the transfer of unnecessary loadgenerated due to a distortion of the leaf spring 13.

[0076] Also, the wing portions 21 a, 21 b of the arm 21 are partlyprovided with the projections 21 e, 21 f facing toward the bottom plate1 c of the base 1 to prevent the leaf spring 13 and the strain detectionsubstrate 2 from a permanent deformation or a breakdown when a loadexceeding the maximum measuring load is applied to the arm 21. When thearm 19 rotates downward about the support pin 22, reaching the specificstroke, the projections 21 e, 21 f come into contact with the bottomplate 1 c of the base 1. On the other hand, in a case of measuring atensile load, projections 19 e, 19 f facing toward the bottom plate 1 cof the base 1, disposed at the end portions of the arm 19, similarlycome into contact with the bottom plate 1 c of the base 1.

[0077] Third Preferred Embodiment

[0078] A weight measuring equipment in the thirs preferred embodiment ofthe present invention will be described with reference to FIG. 10through FIG. 12.

[0079]FIG. 10 is an exploded perspective view of the equipment. FIG. 11is a side sectional view of the equipment. FIG. 12 is a plan view of theequipment. In the description, when simply expressed by wordings such as“up-and-down”, “back-and-forth” and “right-and-left”, they correspond tothe directions of the arrows shown in FIG. 10.

[0080] In the present preferred embodiment, the structure, position, andfunction of base 1 fixed to an object (not shown), strain detectionsubstrate 2, fitting pin 9 are same as those in the first preferredembodiment.

[0081] The equipment of the present preferred embodiment includes afixing pin 11 as a support portion of a leaf spring 33. The fixing pin11 is made of a material that withstand a load higher than the measuringload, the same as the fitting pin 9. The fixing pin 11 is provided witha threaded portion 11 a at an end portion, and an insert portion 1 b ata hexagonal head portion, which is fixed in a tapped hole 12 of the base1. Also, it is so configured that the insert portion 9 b of fitting pin9 and the insert portion 11 b of fixing pin 11 are substantially same inheight when the base 1 is attached with the strain detection substrate 2including the fitting pin 9, and the fixing pin 11.

[0082] As shown in FIG. 11, a guide hole 33 a for a shaft 34 is formednearly in the middle of the leaf spring 33. As a method of making theguide hole 33 a, it is preferable to employ a method of deformationprocessing of the leaf spring 33 as shown in FIG. 10 or a method ofcombination with other member (not shown).

[0083] Also, a dimension of the guide hole 33 a with the shaft 34inserted is made to be substantially free of play in the right-and-left,and the back-and-forth directions.

[0084] There are provided U-shaped notches 33 b, 33 c at both ends ofthe leaf spring 33.

[0085] The notches 33 b, 33 c are respectively inserted into the insertportion 9 b of the fitting pin 9 and the insert portion 11 b of thefixing pin 11 in such a manner that the pins are vertically immovable.Also, the leaf spring 33 is designed to have spring charasteristics inaccordance with the measuring load.

[0086] Arm 35 as a movable member which receives the load of the objectto be measured and is vertically movable is formed of U-shaped plate.Bent wing portions 35 a, 35 b are respectively provided with holes 35 c,35 d so that the arm 35 is able to rotate on the shaft 34.

[0087] A method of assembling these components will be described in thefollowing.

[0088] First, the fitting pin 9 is fixed to the strain detectionsubstrate 2 by the nut 10. Next, the strain detection substrate 2 isfixed to the base 1 with screws 5 a-5 d. Further, the notched portion 33b and the notched portion 33 c of leaf spring 33 are respectivelyinserted into the insert portion 9 b of fitting pin 9 and the insertportion 11 b of the fixing pin 11. Under this condition, the fixing pin11 is fixed in the tapped hole 12 of the base 1. Next, holes 35 c, 35 dand the guide hole 33 a of the leaf spring 33 are aligned, and throughwhich the shaft 34 is inserted, then the leaf spring 33 and the arm 35are assembled via slots 26 a, 26 b formed in the side wall of the base1, and the shaft 34 is fixed with nut 17.

[0089] The operation will be described with reference to FIG. 11.

[0090] When the weight of the object to be measured is applied to thearm 35, the leaf spring 13 suspended between the fitting pin 9 fixed tothe strain detection substrate 2 and the fixing pin 11 fixed to the base1 receives the load and deforms in a state of being supported at bothend. At the time, since the load is concentrated nearly in the middle ofthe leaf spring 33, a half of the weight of the object to be measured isapplied to the action point of the strain detection substrate 2. Astrain is generated in the detection substrate 2 in accordance with theload applied. Accordingly, a resistance of the strain resistor 8changes, and the change of the resistance is computed in a processingcircuit 30 to measure the load.

[0091] Also, in a case of measuring a tensile load, the arm 35 is pulledupward, and the leaf spring 33 deforms upward, then a signal of oppositepolarity is delivered from the strain detection substrate 2.

[0092] As is obvious in the present preferred embodiment, only a half ofthe weight of the object to be measured is applied to the straindetection substrate 2, and thereby, it is possible to improve a loaddetecting resolution.

[0093] Also, since the equipment is unitized, even when the equipment isbuilt in various types of equipment, it is easy to assemble and possibleto reduce the number of assembling steps, and it is unnecessary toadjust the sensor characteristics during the assembly.

[0094] The above configuration involves no problem in the case of normalweight measurement, but when a load exceeding the maximum measuring loadis applied to the equipment via the arm 35, the load is also applied tothe leaf spring 33 and strain detection substrate 2. As a result, thereis a possibility of a permanent deformation or damage of the leaf spring33, or breakdown of the strain detection substrate 2. As acountermeasure, a possible method is to increase the withstand strengthof the leaf spring 33 and the strain detection substrate 2. However,increasing the withstand strength of the leaf spring 33 causes theequipment to increase in size, and increasing the withstand strength ofstrain detection substrate 2 decreases the strain with respect to theload in the measuring range, resulting in lowering of the measuringresolution.

[0095] In order to address this problem, as shown in FIG. 10, slots 26a, 26 b are formed in the side walls of the base 1. The slots 26 a, 26 bare longer in the up-and-down direction than a diameter of the shaft 34,the length of which is set so as to allow the shaft 34 to be movable inthe up-and-down direction for an amount of maximum deformation of theleaf spring 33 at a maximum measuring load applied. Thus, when the loadexceeds the maximum measuring load, the shaft 34 comes in contact withthe inner walls of slots 26 a, 26 b, and stops.

[0096] Accordingly, even when a load or impact load higher than themaximum measuring load is applied, the stopper structure receives theload, and thereby, it is possible to prevent the breakdown of the straindetection substrate 2 or the leaf spring 33.

[0097] Further, as shown in FIG. 12, the dimensions in the widthwisedirection (right-and-left direction in FIG. 10) and lengthwise direction(back-and-forth direction in FIG. 10) of the notches 33 b, 33 c formedin both ends of the leaf spring 33 are set larger than the diameters ofthe insert portion 9 b of fitting pin 9 and the insert portion 11 b offixing pin 11. The purpose is to prevent a force from being directlyapplied to the insert portion 9 b of fitting pin 9 when an abnormalforce is applied back-and-forth and right-and-left direction, during themeasurement or standby mode to the object to be measured, to theequipment, and to the mounting object. For example, when such abnormalload is supposed to be an impact load due to a collision of thevehicles, the load applied is 2,000 kg or more. Even in such a case,though, the equipment is designed not to break down owing to thewithstand strength of the shaft 34 and the base 1, in the course of theimpact application, the impact is absorbed by a little destortions ofthe shaft 34 and other structures. The dimensions of the notches 33 b,33 c of the leaf spring 33 is decided so as to provide a clearance inaccordance with such distortions. Thus, it is possible to prevent thebreakdown of the strain detection substrate 2 even when impacts areapplied to the equipment back-and-forth and right-and-left direction.

[0098] Fourth Preferred Embodiment

[0099] The weight measuring equipment in the fourth preferred embodimentof the present invention will be described with reference to FIG. 13through FIG. 17. FIG. 13 is an exploded perspective view showing anessential portion of the equipment in the present preferred embodiment.FIG. 14 is a plan view of the equipment of the present preferredembodiment. FIG. 15 is a side sectional view of the equipment of thepresent preferred embodiment. FIGS. 16A and 16B are a front view and aside sectional view of a fitting pin showing another configuration inthe present preferred embodiment. FIGS. 17A and 17B are a front view anda side sectional view of a fitting pin showing still anotherconfiguration of the present preferred embodiment.

[0100] In the present preferred embodiment, the base 1 fixed to anobject such as chassis 50 is provided with tapped holes 4 a, 4 b, 4 c, 4d for fixing the strain substrate 2, and tapped holes 12 a, 12 b forfixing leaf spring 43 at positions higher than the tapped holes 4 athrough 4 d. The structure, arrangement, and function of the straindetection substrate 2 are the same as those in the first preferredembodiment.

[0101] Fitting pin 9 is made of a material capable of withstanding aload higher than the measuring load, and is provided with a threadedportion 9 a at the lower part, and a insert portion 9 b at a headthereof. Also, the fitting pin 9 is inserted into the hole 6 of straindetection substrate 2 and fixed by a nut 10.

[0102] A leaf spring 43 is made of a material capable of withstanding aload higher than the measuring load as the same as the fitting pin 9,and a middle beam 43 c at a tip end portion thereof is inserted into theinsert portion 9 b of the fitting pin 9 and is held therein. Also,fixing holes 43 a, 43 b are formed in end beams 43 e, 43 f at both sidesof the leaf spring 43 which is fixed by screws 28 a, 28 b to the tappedholes 12 a, 12 b of the base 1. The insert portion 9 b of fitting pin 9and the middle beam 43 c of the leaf spring 43 are substantially same inheight.

[0103] Also, at another end portion of the leaf spring 43 is formedfixing hole 43 d as a load input portion to be attached to the object tobe measured.

[0104] A method of assembling these components will be described in thefollowing.

[0105] First, the fitting pin 9 is fixed to the strain detectionsubstrate 2 by the nut 10. Next, the strain detection substrate 2 isfixed to the base 1 with screws 5 a, 5 b, 5 c, 5 d. Further, the middlebeam 43 c of the leaf spring 43 is inserted into the insert portion 9 bof the fitting pin 9, and is the leaf spring 43 fastened to the tappedholes 12 a, 12 b of the base 1 by screws 28 a, 28 b through fixing holes43 a, 43 b.

[0106] The operation will be described in the following with referenceto FIG. 15.

[0107] When a weight of the object to be measured is applied to thefixing hole 43 d serving as the load input portion of the leaf spring 43of the weight measuring equipment assembled as described above, a forceis transferred to lift up the fitting pin 9 via the middle beam 43 c ofthe leaf spring 43 fixed to the base 1. Since the fitting pin 9 is fixedto the strain detection substrate 2, a strain is generated in the straindetection substrate 2 by a force to lift up the fitting pin 9.Accordingly, a resistance of the strain resistor 8 changes, and thechange of the resistance is computed in the processing circuit 30 tomeasure the load.

[0108] The end portion of the leaf spring 43 is fork-shaped and only themiddle beam 43 c is held by the fitting pin 9, and therefore, a loadreduced at a specific ratio against the input load is applied to thestrain detection substrate 2. Also, it is possible to reduce the loadapplied to the strain detection substrate 2 at a specific ratio bychanging a length of notched portions or a width of the middle beam 43 cof the fork-shaped portion of the leaf spring 43, or by properlychanging a distance from the fixing holes 43 a, 43 b of the end beams 43e, 43 f at both side ends of leaf spring 43 to the fitting pin 9.

[0109] In the present preferred embodiment, since the two end portionsof the end beams 43 e, 43 f at both side ends of the leaf spring 43 arefastened to the tapped holes 12 a, 12 b, a load in perpendiculardirection to the load detecting direction is hard to be transferred tothe fitting pin 9. Accordingly, it is possible to suppress unnecessaryoutput generated due to the load in the direction perpendicular to theload detecting direction, and to improve the load detecting accuracy.Also, even against an impact given in the direction perpendicular to theload detecting direction, it is possible to prevent the breakdown of thestrain detection substrate 2.

[0110] Further, by forming inner walls in the insert portion 9 b of thefitting pin 9 arcuate in shape as shown in FIGS. 16A, 16B, orsemicircular as shown in FIGS. 17A, 17B, a contacting portion betweenthe inner wall formed in the insert portion 9 b of the fitting pin 9 andthe middle beam 43 c of leaf spring 43 becomes a line ora point.Therefore, it is possible to reduce a friction between the twocomponents and also to suppress a transfer of unnecessary load generateddue to a twisting or the like. As a result, the stability of the sensoroutput against the load may be further enhanced.

[0111] Also, since the equipment of the present preferred embodiment isunitized, when the equipment is attached to a vehicle seat, for example,it is possible to reduce the number of assembling steps and it isunnecessary to adjust the sensor characteristics during assembly.

[0112] Fifth Preferred Embodiment

[0113] The weight measuring equipment in the fifth preferred embodimentof the present invention will be described with reference to FIG. 18through FIG. 22.

[0114]FIG. 18 is an exploded perspective view of the equipment in thepresent preferred embodiment. FIG. 19 is a plan view of the equipment.FIG. 20 is a side sectional view. FIGS. 21A, 21B are a front view and aside view of a fitting pin showing another configuration in the presentpreferred embodiment. FIGS. 22A, 22B are a front view and a side view ofa fitting pin showing still another configuration of the presentpreferred embodiment.

[0115] In the present preferred embodiment, same components as in thefourth preferred embodiment are given the same numerals, and thedetailed descriptions of the same are omitted, and only differences willbe described in detail.

[0116] As shown in FIG. 18, in the present preferred embodiment, themiddle beam 43 c of the leaf spring 43 in the fourth preferredembodiment 4 is divided into U-shape, while the insert portion 9 b ofthe fitting pin 9 is H-shaped in section. This configuration makes iteasier to hold the middle beam 43 c on the fitting pin 9, and simplifiesthe shape of the fitting pin 9, thereby improving the workability.

[0117] Also, same as in the fourth preferred embodiment, it ispreferable to form the inner walls of the insert portion 9 b of fittingpin 9 arcuate in shape as shown in FIGS. 21A and 21B, or semicircular asshown in FIGS. 22A and 22B. By this configuration, it is possible toreduce the friction between the two components and to suppress thetransfer of unnecessary load generated due to a twisting or the like. Asa result, the stability of sensor output against the load may be furtherenhanced.

[0118] Sixth Preferred Embodiment

[0119] The weight measuring equipment in the sixth preferred embodimentof the present invention will be described with reference to FIG. 23through FIG. 25. FIG. 23 is an exploded perspective view showing thesixth preferred embodiment. FIG. 24 is a plan view, and FIG. 25 is aside sectional view of the equipment.

[0120] In the present preferred embodiment, same components as in thefourth preferred embodiment are given the same numerals, and thedetailed descriptions of same are omitted, and only differences will bedescribed in detail.

[0121] In the present preferred embodiment, as shown in FIG. 23, a loadinput end side of leaf spring 43 is divided into three portions, andside holding portion 43 g, 43 h and middle holding portion 43 i are bentopposite to each other so that the leaf spring 43 can be held by linkpin 38. And, there is provided arm 39 having fixing hole 39 c to beattached to a load applied portion, which is suspended by the link pin38 via holes 39 a, 39 b. Also, in the side walls of the base 1 areformed slots 27 a, 27 b for vertically guiding the link pin 38 and forcontrolling an amount of destortion of the leaf spring pin 43.

[0122] In the equipment configured as described above, since the arm 39to which a weight of the object to be measured is applied is supportedby the link pin 38, the arm 39 always receive the load in a parallelstate, and can correctly transfer the load to the strain detectionsubstrate 2 via the leaf spring 43.

[0123] Also, regarding a permanent deformation or a breakdown of theleaf spring 43 and the strain detection substrate 2 with a loadexceeding the maximum measuring load, they are prevented by theconfiguration where the link pin 38 comes in contact with the endportions of slots 27 a, 27 b formed in the side walls of the base 1 andfunction as stoppers.

[0124] Seventh Preferred Embodiment

[0125] A weight measuring equipment in the seventh preferred embodimentof the present invention will be described with reference to FIG. 26through FIG. 28. FIG. 26 is an exploded perspective view showing thepresent preferred embodiment. FIG. 27 is a plan view, and FIG. 28 is aside sectional view of the equipment.

[0126] In the seventh preferred embodiment same components as in thefourth preferred embodiment are given the same numerals, and thedetailed descriptions of the same are omitted, and only differences willbe described in detail.

[0127] As shown in FIG. 26, a load input end side of leaf spring 43 isprovided with a semicircular projection 36. An arm 40 is substantiallybox-shaped, and at a top thereof is formed a hole 40 c to be attached toa load applied portion. Also, V-shaped ribs 37 a, 37 b are provided atan end portion of the base 1. The arm 40 holds the semicircularprojection 36 formed on the leaf spring 43 in such manner as to enclosethe semicircular projection 36, and is disposed in a substantiallyparallel arrangement to the V-shaped ribs 37 a, 37 b provided at the endportion of the base 1.

[0128] In the equipment having a configuration as described above, sincethe arm 40 to which the weight of the object to be measured is appliedis supported by the semicircular projection 36 formed at the load inputside of the leaf spring 43, and always receive the load at one point, itis possible to avoid unnecessary output generated due to a twisting orthe like applied to the arm 40.

[0129] Also, as a stopper structure against a load or impact load higherthan the maximum measuring load, a clearance is provided between thebottom inner surface of arm 40 and the ribs 37 a, 37 b for an amount ofmaximum displacement of the leaf spring 43 for the maximum measuringload against an upper displacement of the arm 40 in the up-and-downdirection. Also, a clearance is provided between a bottom outer surfaceof arm 40 and the base surface of base 1 for an amount of maximumdisplacement of the leaf spring 43 for the maximum measuring loadagainst the lower displacement of the arm 40 in the up-and-downdirection. In this way, even when a load or an impact load higher thanthe maximum measuring load is applied in the up-and-down direction, thestopper structure receives the load, protecting the strain detectionsubstrate 2 from excessive load, and prevents the breakdown of thestrain detection substrate 2 and the leaf spring 43.

[0130] Eighth Preferred Embodiment

[0131]FIG. 29 is a side view for describing a vehicle seat attached withany one of the equipments shown in FIG. 1, FIG. 4, FIG. 10, FIG. 13,FIG. 18, FIG. 23 and FIG. 26.

[0132] A seat truck 45 is disposed beneath a seat (such as a passengerseat) 46. The load input end side of the equipment 44 of the presentinvention is attached by bolts and nuts (not shown) to the seat truck45. On the other hand, the base 1 of the equipment 44 is similarly fixedby bolts and nuts (not shown) to chassis 50. The equipments 44 aredisposed at a front and a rear ends of the seat trucks 45 so as tocorrespond to the four bottom corners of the seat 46. In this condition,the weight of the person actually sitting on the seat 46 is measured bythe equipments 44 disposed at four portions and computed to judge theweight. At the time, a weight of the seat 46 itself is compensated bypreviously setting or storing in a memory. As described above, since theequipments 44 are disposed at the front and the rear ends of the seattrucks 45 in such manner as to correspond to the four bottom corners ofthe seat 46, it is possible to judge the weight even when the positionof the person sitting on the seat is changed, and also, to estimate thesitting position by comparing the loads.

[0133] In the above description, an example of disposing four equipmentsat the bottom of the seat 46 has been described, but the number of theequipments disposed is not limit to four. It is also preferable toinstall one or two equipments at a side opposite to the front or rearsupport portion of the seat which is rotatably supported, and further,to increase the number of the equipments disposed in order to improve ameasuring accuracy.

[0134] Also, similar results can be obtained by installing the equipment44 between the seat 46 and the seat truck 45, although the configurationis not shown. In this case, since the weight of the seat truck 45 is notsuperposed on the strain detection substrate 2, the weight to becorrected is less, improving the computing or previous setting accuracy,and as a result, the accuracy of detection can be enhanced.

[0135] As described above, it is possible to realize reliable personweight measuring equipment by disposing an appropriate number of theequipments of the present invention under a vehicle seat.

Industrial Applicability

[0136] According to the present invention, it is possible to obtain aweight measuring equipment reduced in a load applied to the straindetection substrate and improved in detecting resolution. Also, sincethe weight measuring equipment is unitized, it can be easily built invarious types of equipment including seats for vehicles.

1. A weight measuring equipment comprising: a base fixed to an object tobe mounted; a strain detection substrate attached to said base; afitting pin fixed to said strain detection substrate; an arm rotatablyattached to said base by a support pin; and a leaf spring, said leafspring fixed with one end to said arm and supported with another end bysaid fitting pin.
 2. The weight measuring equipment of claim 1, furthercomprising a second arm, said second arm receiving a load of an objectto be measured with one end, and fixed to said arm by a link pin withanother end.
 3. The weight measuring equipment of claim 1, wherein apart of one of said arm and said second arm comes into contact with saidbase when a load exceeds a maximum measuring load of said weightmeasuring equipment.
 4. The weight measuring equipment of claim 1,wherein said leaf spring is provided with a predetermined clearance fromsaid fitting pin at a portion supported by said fitting pin.
 5. Theweight measuring equipment of claim 2, wherein said link pin issupported by a guide hole to be movable in a direction perpendicular toa bottom of said base, said guide hole formed in said base, and saidlink pin is supported by a slide hole to be movable in a directionparallel to the bottom of said base, said slide hole formed in said arm.6. The weight measuring equipment of claim 1, wherein an inner wall ofsaid fitting pin at a portion for supporting said leaf spring has one ofarcuate shape and semicircular shape.
 7. The weight measuring equipmentof claim 1, further comprising a fixing pin fixed to said base, whereinsaid leaf spring is supported by said fitting pin and said fixing pin atboth ends thereof, and said arm is connected nearly to a middle portionof said leaf spring and is movable in up-and-down direction by receivinga weight of an object to be measured.
 8. The weight measuring equipmentof claim 7, wherein said leaf spring is provided with a predeterminedclearance from said fixing pin at a portion supported by said fixingpin.
 9. The weight measuring equipment of claim 7, wherein a shaft whichsupports said leaf spring is movable in up-and-down direction in a slotformed in said base.
 10. The weight measuring equipment of claim 7,wherein said shaft comes into contact with an inner wall of said slotwhen a load exceeds a maximum measuring load of said weight measuringequipment.
 11. The weight measuring equipment of claim 1, wherein saidleaf spring is provided with fork-shaped three beams at one end, andanother end of said leaf spring is a load applied portion for receivinga load, said fitting pin has an insert portion for holding a middle beamof said three beams, and ends of the beams at both sides of said threebeams are fixed to said base, respectively.
 12. The weight measuringequipment of claim 11, wherein the middle beam of said leaf spring heldby said fitting pin is one of straight and divided in shape.
 13. Theweight measuring equipment of claim 11, wherein said middle beam isnarrower in width than the beams at both sides.
 14. The weight measuringequipment of claim 11, wherein a inner wall of a portion for supportingsaid middle beam of said fitting pin is one of arcuate and semicircularin shape.
 15. The weight measuring equipment of claim 11, wherein theload applied portion side of said leaf spring is divided into threeportions, both of side portions and middle portion of said threeportions divided being bent opposite to each other and held by a linkpin, and said link pin supports an arm provided with a fixing hole forthe load applied portion.
 16. The weight measuring equipment of claim11, wherein a semicircular projection is disposed at the load appliedportion side of said leaf spring, and said arm is arranged so as to holdsaid semicircular projection.
 17. The weight measuring equipment ofclaim 11, wherein a stopper for controlling an amount of deformation ofsaid leaf spring is provided.
 18. The weight measuring equipment ofclaim 1, wherein said base is fixed to the chassis side of a vehicle,and one of said arm and said second arm is connected to a seat truckbottom of a vehicle seat.
 19. The weight measuring equipment of claim 1,wherein said base is fixed to a seat truck of a vehicle seat, and one ofsaid arm and said second arm is connected to the vehicle seat. 20.Person weight measuring equipment comprising the the weight measuringequipment of any one of claims 1 through 19, the base of said weightmeasuring equipment being fixed to a chassis side, and one of the armand the second arm of said weight measuring equipment being fixed to aseat truck bottom of a vehicle seat, wherein a seat weight seat andperson weight is measured by a load detected by said weight measuringequipment.
 21. The person weight measuring equipment of claim 20,wherein said weight measuring equipment is installed at four corners ofsaid vehicle seat.
 22. Person weight measuring equipment comprising thethe weight measuring equipment of any one of claims 1 through 19, thebase of said weight measuring equipment being fixed to a seat truck of avehicle seat, and one of the arm and the second arm of said weightmeasuring equipment being fixed to said vehicle seat, wherein a seatweight seat and person weight is measured by a load detected by saidweight measuring equipment.
 23. The person weight measuring equipment ofclaim 22, wherein said weight measuring equipment is installed at fourcorners of said vehicle seat.